The long term objective of this project is to analyze the role of the context in the acquisition and performance of learned behavior. The aims of this proposal are to study how hierarchically structured contexts influence behavior in Pavlovian conditioning paradigms. Specifically, the experiments aim to 1) analyze the influence of extra-experimental contexts on the behavior within experimental sessions; 2) study the influence of experimental contexts on behavior controlled by events that occur within experimental episodes; and 3) investigate the influence of local contexts defined within experimental sessions on events embedded in the local context. Contextual stimuli modulate the frequency, intensity and situational control of conditioned physiological and behavioral reactions. The outcomes of this research, therefore, have broad implications for the understanding of basic behavioral processes.